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plugins/helo: added RFC 5321 notes

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Matt Simerson 2013-03-10 23:22:44 -04:00
parent 6a0fa13ee1
commit b9750ee5bf
1 changed files with 20 additions and 3 deletions
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plugins/helo
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@ -75,6 +75,9 @@ Make sure the HELO hostname has an A or AAAA record that matches the senders
IP address, and make sure that the senders IP has a PTR that resolves to the IP address, and make sure that the senders IP has a PTR that resolves to the
HELO hostname. HELO hostname.
Per RFC 5321 section 4.1.4, it is impermissible to block a message I<soley>
on the basis of the HELO hostname not matching the senders IP.
Since the dawn of SMTP, having matching DNS has been a minimum standard Since the dawn of SMTP, having matching DNS has been a minimum standard
expected and oft required of mail servers. While requiring matching DNS is expected and oft required of mail servers. While requiring matching DNS is
prudent, requiring an exact match will reject valid email. While testing this prudent, requiring an exact match will reject valid email. While testing this
@ -121,10 +124,10 @@ address literal. When I<policy rfc> is selected, all the lenient checks and
the following are enforced: is_not_fqdn, no_forward_dns, and no_reverse_dns. the following are enforced: is_not_fqdn, no_forward_dns, and no_reverse_dns.
If you have Windows users that send mail via your server, do not choose If you have Windows users that send mail via your server, do not choose
I<policy rfc> without settings I<reject naughty> and using the B<naughty> I<policy rfc> without setting I<reject naughty> and using the B<naughty>
plugin. Windows PCs often send unqualified HELO names and will have trouble plugin. Windows PCs often send unqualified HELO names and will have trouble
sending mail. The B<naughty> plugin defers the rejection, and if the user sending mail. The B<naughty> plugin defers the rejection, giving the user
subsequently authenticates, the rejection is be cancelled. the opportunity to authenticate and bypass the rejection.
=head3 strict =head3 strict
@ -187,6 +190,20 @@ that is not in FQDN form is no more than a local alias. Local aliases MUST
NOT appear in any SMTP transaction. NOT appear in any SMTP transaction.
=head1 RFC 5321
=head2 4.1.4
An SMTP server MAY verify that the domain name argument in the EHLO
command actually corresponds to the IP address of the client.
However, if the verification fails, the server MUST NOT refuse to
accept a message on that basis. Information captured in the
verification attempt is for logging and tracing purposes. Note that
this prohibition applies to the matching of the parameter to its IP
address only; see Section 7.9 for a more extensive discussion of
rejecting incoming connections or mail messages.
=head1 AUTHOR =head1 AUTHOR
2012 - Matt Simerson 2012 - Matt Simerson